function zhuan(obj){
    var str=''
    for(var key in obj){
        str +=`${key}=${obj[key]}&`
    }
    return str.slice(0,str.length-1)
}
function ajax(method,url,can){
    return new Promise((resolve,reject)=>{
        var xhr=new XMLHttpRequest()
        xhr.open(method,method=='get' ? url+'?'+zhuan(can) : url)
        xhr.onreadystatechange=function(){
            if(xhr.readyState==4){
                resolve(JSON.parse(xhr.responseText))
            }
        }
        xhr.setRequestHeader('content-type', 'application/x-www-form-urlencoded');
        xhr.send(method=='get' ? null : zhuan(can))
    })
}